A New Season for Cardiac Troponin Assays: It’s Time to Keep a Scorecard

Advancements in cardiac troponin (cTn)2 assay tech-nology have created a conundrum for clinicians and laboratory scientists, whomust determinewhich assays are best for optimal patient care. Unfortunately, few resources are available to guide the medical and scien-tific communities in this regard. International guide-lines (1–3) have defined an increased cTn above the 99th percentile limit as an abnormal result; what is lacking, unfortunately, is an approach to define this limit across the heterogeneity of the assays. In spite of the evidence-based literature demonstrating that cTn concentrations tend to increase in individuals 60 years old (4), 99th percentile reference limits are often determined across wide age ranges using subjects as old as 70 years (convenience samples). Further frustrating the problem of selecting relevant reference subjects, in clinically defined “normal ” individuals without known cardiovascular disease, increased cTn concentrations are indicative of a significantly higher risk of death (4, 5). The occurrence of such individuals in reference populations may reflect inadequate screening for co-morbidities at the time of sample acquisition. Given such problems, a majority of laboratories either accept the manufacturer’s reference limit from the US Food and Drug Administration (FDA)-cleared package in-sert, perform an underpowered normal range study to establish a reference limit, or accept a reference limit published in the literature. To validate cTn assays, however—to level the playing field for all users—is necessary for the best patient care. cTnI and cTnT are established as the standard bi-omarkers for the detection of myocardial injury and prognostic evaluation of patients with acute coronary syndrome (ACS) and without (1–3). The consensus guidelines from theGlobal Task Force for theUniversal